Although it may be applied to many energy supply systems, the present invention and the underlying problems are explained in detail below with respect to energy supply systems for aircraft.
In modern aircraft and spacecraft, especially in modern passenger aircraft, demand for electrical energy continues to rise. One reason for this, inter alia, is the implementation of the so-called more-electric-aircraft concept. In this concept, previously hydraulically or pneumatically operated systems are replaced by purely electrically operated systems. This thus avoids energy conversion losses. Transmission losses from electrical systems are also generally lower than from hydraulically or pneumatically operated systems. Electrical systems also have a high level of diagnostic capability.
An aircraft has energy supply systems in order to generate and provide the necessary electrical energy. These energy supply systems obtain the electrical energy by means of generators, for example, which are provided on the aircraft engines. Alternatively, or additionally, batteries or fuel cells may also be used as energy sources. The output voltage of such an energy supply system is load-dependent and is thus not constant. Converters which are specifically intended for this purpose are used, which convert an output voltage of the energy supply system into a supply voltage which is suitable for operating the various electrical systems in the aircraft. Traditional converters are designed to operate over the entire output voltage range and power range of the respective energy source. This means that the converter is operated both when the energy source is idle with maximum voltage and minimum power, and with minimal output voltage and maximum electrical power.
Such traditional converters have a standard efficiency of approximately 94%. With an electrical output power of 60 kW, the power lost by the converter is approximately 3.6 kW, which is equivalent to a relatively poor efficiency rate for the energy supply system. In addition, cooling needs to be provided for the converter to dissipate or cool the relatively high power loss of up to 3.6 kW which is expressed as heat loss. Provision of such a cooling system increases the weight of the converter to an undesirable extent.